This invention generally relates to pneumatic springs and more particularly to an improved air spring having the capability of being dual acting, that is, being capable of providing both compression or extension forces. This invention is particularly useful in automotive and truck suspension applications where it may be desirable to change the spring rate of the air spring independent of the load being supported by the air spring. It is also useable to lift axle suspensions when such suspension members are unneeded for support and still provide the load carrying capability when the axle is in use. It is also used to provide positive driving force in both the compression and extension directions as in mechanical servo actuators.